Electrical contact plug or pin



1936- E. KLEINMANN E1: AL 2,0 4,

ELECTRICAL CONTACT PLUG OR PIN Filed D96. 18, 1955 Fig. 1.

Fig.2.

j g7 IIVVE'IVITORSH W ATTORNEY Patented Dec. 15, 1936 UNITED STATES PATENT OFFICE Ernst Kieinmann and Alfred Mendel,

Liehtenbcrg, Germany Berlin- Application December 18, 1933, Serial No. 703,007 In Germany December 21, 1932 10 Claims.

This invention relates to electrical contact plugs or pins, hereinafter referred to as "electrical contact pins", and more particularly to tubular contact pins of the kind that are slit longitudinally to enable the cylinder from which they are made to be given a slight bulge between the ends to form resilient contact surfaces. They are then referred to as "banana plugs. The contact area in such banana plugs is limited because contact takes place only along an annular line at the point of maximum diameter of the bulge. Moreover, they are easily able to tilt in the socket. The chief object of the invention is to provide a contact pin that will be suitable for use with larger currents than the usual banana plug type of pin and which will remain more firmly in position in the socket.

According to the invention, a. slit tubular electrical contact 'pin has two or more bananagradually increases to a maximum and gradually falls to a minimum at least twice in its length. By providing two or more such enlargements in this way, the contact area may be made aslarge as is desired and the pin cannot easily tilt about its axis. The diameter of the enlargement adjacent the end adapted to enter a socket may be greater or less' than the diameter. of the other enlargements for the purposes explained hereafter.

In order that the invention may be clearly understood and readily carried into efiect, it will now be more fully described with reference to the three figures of the accompanying drawing,

each of which figures is a side elevation of an example oi an electrical contact pin provided with two enlargements in accordance with the invention. All of the pins illustrated in the drawing are formed by rolling up into substan- 40 tially cylindrical form a slit piece of sheet metal. It is to be understood, however, that a pin according to the invention could be made by boring .and slitting a solid rod. The pins illustrated are intended for use as the contact pins of thermionic valves.

In all the figures, 4 is the upper cylindrical end of the pin and 3 a bead which may serve to limit the extent to which the pin enters its socket.

The slits I of one enlargement are separate from those 6 of the other. It will be noted that the surface of the body of each pin is formed as a surface of revolution produced by revolving a shaped enlargements; that is to say, its diameter In the pin of Figure 1 the two banana-shaped enlargements I and 2 are 01 the same diameter.

(Cl. 17H63) sinuous line about the axis of the pin, the sinuous line having at least two convex portions and at least one intermediate concave portion connecting the convex portions.

In order to facilitate the introduction into its socket of a pin having two, or more enlargements according to the invention, the diameter of the enlargement 2 nearest the lower end of the pin, i. e. the end that is introduced into the socket, may be of a different diameter from that of the other enlargement I (or other enlargements). A pin in which this enlargement is smaller is shown in Figure 2. When such a pin is introduced into its socket, the lower enlargement 2 does not at first do more than make only very loose contact with the socket wall. When the pin is pushed further in, however, the upper enlargement i is pressed into the socket, and this, on account of its greater diameter, and the fact that the pin is made from thin sheet metal, becomes compressed and thus simultaneously spreads the lower enlargement so that both enlargements then give good contact along a fiat surface. This pin is particularly suitable for use with a coned socket.

In the pin shown in Figure 3, the lower .enlargement 2 is of a somewhat larger diameter than the other I (or others). When such apin is pushed into its socket, the lower enlargement 2 immediately makes good contact and rubs smooth the possibly oxidized inner surface of the socket. At the same time the lateral pressure thus exerted on the lower enlargement 2 causes the upper and smaller enlargement I to spread to such an extent that it also makes good contact with the socket, when the pin is pushed right home.

We claim:-

1. A thin-walled tubular electrical contact pin the diameter of which gradually increases to a maximum and gradually falls to a minimum at least twice in its length to form at least two gently curved banana-shaped enlargements of equal diameters each of which has at least one longitudinal slit terminating short of the slit in the other and short of the end of the pin so that lateral compression of one of which enlargements leads to lateral expansion of another.

2. A thin-walled tubular electrical contact pin the diameter of which gradually increases to a maximum and gradually falls to a minimum at least twice in its length to form at least two gently curved banana-shaped enlargements each of which is provided with at least one longitudenlargement and terminating short of the adjacent end of the pin so that lateral compression of one of which enlargements leads to lateral expansion of another.

3. A thin-walled tubular electrical contact pin the diameter of which gradually increases to a maximum and gradually falls to a minimum at least twice in its length to form at least two gently curved banana-shaped enlargements each of which is provided with at least one longitudinal slit terminating short of the longitudinal slit in the other enlargement and short of the adjacent end of the pin so that lateral compression of one of which enlargements leads to lateral expansion of another.

4. A thin-walled electrical contact pin consisting of a sheet of metal provided with at least two longitudinal slits bent around into tubular form said tube having its diameter gradually increased to a maximum and gradually reduced to a minimum at least twice in its length to form at least two gently curved banana-shaped enlargements each of which is provided with one of said longitudinal slits terminating short of the longitudinal slit in the other enlargement and short of the adjacent end of the pin so that lateral compression of one of which enlargements leads to lateral expansion of another.

5. A thin-walled tubular electrical contact pin the diameter of which gradually increases to a maximum and gradually falls to a minimum at least twice in its length to form at least two gently curved banana-shaped enlargements each of which has at least one longitudinal slit-while the pin is continuous circumferentially at each end and between said enlargements so that lateral compression of one of said enlargements leads to lateral expansion of another.

6. A thin-walled electrical contact pin consisting of a sheet of metal provided with at least two slits bent around into tubular form and so shaped that its diameter gradually increases to a maximum and gradually falls to a minimum at -least twice in its length to form at least two gently curved banana-shaped enlargements each of which is provided with at least one longitudinal slit while the pin is continuous circumferentially at each endand between said enlargements except for the line of abutment of the contiguous ends of said sheet.

7. A thin-walled tubular electrical contact pin the diameter of which gradually increases to a maximum and gradually falls to a minimum at least twice in its length to form at least two gently curved banana-shaped enlargements each of which has at least one longitudinal slit, corresponding slits of the enlargements being in alinement and falling short of one another and of the ends of the pin so that lateral compression of one of said enlargements leads to lateral expansion of the other.

8. An electrical contact pin including a thin tubular bodyhaving its outer surface constituting a surface of revolution generated by the revolution of a sinuous line having at least two convex arcuate portions and at least one concave portion connecting the adjacent ends of the convex portions, said line being revolved about the axis of'the pin as the axis of the surface whereby the body of the pin is provided with alternate portions having relatively large maximum and relatively small minimum diameters respectively, each of said relatively large diameter portions being provided with at least one longitudinal slit, said slits having their adjacent ends spaced longitudinally of said body and the ends of the slits adjacent the ends of the body being in spaced relation to the respective ends.

9. An-electrical contact pin including a thin" tubular body having its outer surface constituting a surface of revolution generated by the revolution of a sinuous line having at least two convex arcuate portions and at least one concave portion connecting the adjacent ends of the convex portions, said line being revolved about the axis of the pin as the axis of the surface whereby the body of the pin is provided with alternate portions having relatively large maximum and relatively small minimum diameters respectively,

each of said relatively large diameter portions being provided with at least one longitudinal slit, said slits having their adjacent ends spaced longitudinally of said body and the ends of the slits adjacent the ends of the body being in spaced relation to the respective ends, the portions of relatively large diameter having equal maximum diameters.

10. An electrical contact pin including a thin tubular body having its outer surface constituting a surface of revolution generated by the and the ends of the slits adjacent the ends of the body being in spaced relation to the respective ends, the portion of relatively large diameter adjacent one end of the pin being of greater maximum diameter than the corresponding portion adjacent the other end of the pin.

ERNST KLEINMANN. 

